VMP reports consultant fees from Bluebird Bio; advisory board fees from Bluebird Bio, Bristol Myers Squibb and Vertex Pharmaceuticals; and speaker bureau fees from Novartis. EA reports being a Data Monitoring Committee chair for Vertex Pharmaceuticals and Bristol Myers Squibb; advisory board fees from Regeneron and Novartis; speaker bureau fees from Bristol Myers Squibb and Sanofi; and honoraria from Sanofi. LO reports consultancy fees from Pfizer and Vertex Pharmaceuticals; advisory boards from Chiesi, Vertex Pharmaceuticals and Novartis; and speakers fees from Pfizer and Novartis. The remaining authors have no competing interests to disclose. All competing interests are outside the present work.